[X86] Optimize avx2 vgatherqps for v2f32 with v2i64 index type.

Normal type legalization will widen everything. This requires forcing 0s into the mask register. We can instead choose the form that only reads 2 elements without zeroing the mask.

llvm-svn: 319406

1 files changed, 12 insertions, 7 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 110af66b422..a21145f0755 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -1127,6 +1127,9 @@ X86TargetLowering::X86TargetLowering(const X86TargetMachine &TM,
     }
 
     if (HasInt256) {
+      // Custom legalize 2x32 to get a little better code.
+      setOperationAction(ISD::MGATHER, MVT::v2f32, Custom);
+
       for (auto VT : { MVT::v4i32, MVT::v8i32, MVT::v2i64, MVT::v4i64,
                        MVT::v4f32, MVT::v8f32, MVT::v2f64, MVT::v4f64 })
         setOperationAction(ISD::MGATHER,  VT, Custom);
@@ -1360,11 +1363,6 @@ X86TargetLowering::X86TargetLowering(const X86TargetMachine &TM,
         setOperationAction(ISD::CTPOP, VT, Legal);
     }
 
-    // Custom legalize 2x32 to get a little better code.
-    if (Subtarget.hasVLX()) {
-      setOperationAction(ISD::MGATHER, MVT::v2f32, Custom);
-    }
-
     // Custom lower several nodes.
     for (auto VT : { MVT::v4i32, MVT::v8i32, MVT::v2i64, MVT::v4i64,
                      MVT::v4f32, MVT::v8f32, MVT::v2f64, MVT::v4f64 })
@@ -24863,7 +24861,7 @@ void X86TargetLowering::ReplaceNodeResults(SDNode *N,
   }
   case ISD::MGATHER: {
     EVT VT = N->getValueType(0);
-    if (VT == MVT::v2f32 && Subtarget.hasVLX()) {
+    if (VT == MVT::v2f32 && (Subtarget.hasVLX() || !Subtarget.hasAVX512())) {
       auto *Gather = cast<MaskedGatherSDNode>(N);
       SDValue Index = Gather->getIndex();
       if (Index.getValueType() != MVT::v2i64)
@@ -24873,10 +24871,17 @@ void X86TargetLowering::ReplaceNodeResults(SDNode *N,
       SDValue Src0 = DAG.getNode(ISD::CONCAT_VECTORS, dl, MVT::v4f32,
                                  Gather->getValue(),
                                  DAG.getUNDEF(MVT::v2f32));
+      if (!Subtarget.hasVLX()) {
+        // We need to widen the mask, but the instruction will only use 2
+        // of its elements. So we can use undef.
+        Mask = DAG.getNode(ISD::CONCAT_VECTORS, dl, MVT::v4i1, Mask,
+                           DAG.getUNDEF(MVT::v2i1));
+        Mask = DAG.getNode(ISD::SIGN_EXTEND, dl, MVT::v4i32, Mask);
+      }
       SDValue Ops[] = { Gather->getChain(), Src0, Mask, Gather->getBasePtr(),
                         Index };
       SDValue Res = DAG.getTargetMemSDNode<X86MaskedGatherSDNode>(
-        DAG.getVTList(MVT::v4f32, MVT::v2i1, MVT::Other), Ops, dl,
+        DAG.getVTList(MVT::v4f32, Mask.getValueType(), MVT::Other), Ops, dl,
         Gather->getMemoryVT(), Gather->getMemOperand());
       Results.push_back(Res);
       Results.push_back(Res.getValue(2));